Benedict Cumberbatch will star in an HBO movie about Brexit. Here’s why the film is controversial.

Brits want an official investigation into the Brexit Leave campaign. They’re getting an HBO drama instead.

On Friday, HBO revealed the trailer for its upcoming film Brexit, a Toby Haynes-directed drama about the 2016 Vote Leave campaign that “goes behind the scenes, revealing the personalities, strategies and feuds of the Leave and Remain campaigns,” according to HBO.

Set to premiere on HBO and the United Kingdom’s Channel 4 on January 19, Brexit aims to be a dramatic retelling of the highly advanced political campaign that encouraged Brits to vote to leave the European Union — a campaign whose tactics, motivations, and repercussions are yet to be fully understood.

The film, an international co-production with BBC Studios, Channel 4, and House Productions, stars Benedict Cumberbatch as the man who spearheaded that campaign: Dominic Cummings.

Cummings, whom the trailer introduces by saying “Meet the man behind Brexit,” was the Campaign Director for Vote Leave from its creation in October 2015, and is credited with coming up with the slogan “Take back control.” (Observer columnist Nick Cohen recently called him “the most important contemporary figure 99 percent of the population have never heard of.”)

In the trailer, Cummings appears to stoke racial resentment, asking, “Is it immigration? You can be honest. Is it race? Which countries don’t you like?” — while writing “Turkey” on a door covered in notes and explaining the Leave movement as about a desire to “return to a time when we knew our place.”

The trailer references the advanced, questionable data tactics the campaign employed, with Cumberbatch’s Cummings discussing “hacking the electoral system” and building a social media strategy that “will re-stack the odds in our favor.”

The film’s timing is controversial, with the UK deeply divided over how to leave the EU, and whether the decision to do so was undertaken fairly.

A number of Brits have taken to Twitter to express their anger at the film. Carole Cadwalladr, a journalist who has conducted extensive investigations into Vote Leave, compared it to the UK making a film about special counsel Robert Mueller’s investigation into Russian interference in the 2016 US presidential election as it unfolds.

What investigation?

As Brexit negotiations crawl to a standstill, details of the tactics the Leave campaign used are still being uncovered. There is no single “investigation” into the campaign as there is with Donald Trump, although Cadwalladr — among others — has suggested that Britain needs its own Mueller-style inquiry.

Fair Vote UK is preparing to launch a legal challenge over the government’s refusal to hold an inquiry into the “irregular and unlawful conduct” that may have influenced the result, including Russian disinformation and breaches of electoral spending laws.

The Leave campaign has been investigated, however, by the UK Electoral Commission over its use of funds and data. In July, an Electoral Commission probe found that Vote Leave had broken electoral law, exceeding its £7 million spending limit by funneling money through another pro-Brexit group, BeLeave (the official leave and remain campaigns were limited in what they were allowed to spend). With the referendum resulting in a narrow 51.9 percent victory for Leave, some argue that this overspending could have been decisive.” (One conservative MP has made multiple allegations over the Remain campaign’s spending, but these have all been rejected by the Electoral Commission).

Brits in the Remain camp have also drawn attention to the £2.7 million the Leave campaign spent on data services from Aggregate IQ, a Canadian digital marketing firm linked to Cambridge Analytica. Cambridge Analytica whistleblower Chris Wylie has claimed that the firm helped “cheat” the Brexit vote, along with the US presidential election, though Facebook last month claimed their was no evidence that data was used in UK campaigns.

Dominic Cummings, the man at the heart of HBO’s film, has refused to appear before a House of Commons committee inquiry into fake news, which has also summoned the former head of Cambridge Analytica, Alexander Nix.